The present disclosure relates to processes for formation of latex resins. In embodiments, the below described processes may be accomplished without the use of a solvent.
Processes for forming toner compositions for use with electrostatographic, electrophotographic or xerographic print of copy devices have been previously disclosed. For example, methods of preparing an emulsion aggregation (EA) type toner are known, and toners may be formed by aggregating a colorant with a latex polymer formed by batch or semi-continuous polycondensation. U.S. Pat. No. 6,063,827, the disclosure of which is hereby incorporated by reference in its entirety, is directed to a polycondensation process for the preparation of an unsaturated polyester. U.S. Pat. No. 5,227,460, the disclosure of which is hereby incorporated by reference herein in its entirety discloses partially cross-linked resins that can be selected for the preparation of heat fixable toners.
Other examples of emulsion/aggregation/coalescing processes for the preparation of toners are illustrated in U.S. Pat. Nos. 5,290,654, 5,278,020, 5,308,734, 5,370,963, 5,344,738, 5,403,693, 5,418,108, 5,364,729 and 5,346,797, the disclosures of each of which are hereby incorporated herein by reference in their entirety. Other processes are disclosed in U.S. Pat. Nos. 5,348,832, 5,405,728, 5,366,841, 5,496,676, 5,527,658, 5,585,215, 5,650,255, 5,650,256, and 5,501,935, the disclosures of each of which are hereby incorporated herein by reference in their entirety.
As discussed above, latex polymers utilized in the formation of EA type toners may be formed by batch, semi-continuous or continuous polymerization. Batch processes for producing these polymers may include the bulk polycondensation of resins in a batch reactor at an elevated temperature. Semi-continuous and continuous processes may include polycondensation reactions of resins undertaken in a series of reaction vessels connected in series. After the resulting resin is cooled, crushed and milled, the resin is dissolved in a solvent. The dissolved resin is then subjected to emulsification to prepare a polymer latex. Emulsification may include combining with stirring of the resin with organic solvents, such as methyl ethyl ketone and/or isopropyl alcohol to produce a homogenous organic phase. A fixed amount of base solution, such as ammonium hydroxide, may be added to the organic phase to neutralize acid end groups on the polymer chain, followed by the addition of deionized water to form a uniform dispersion of polymer particles in water through phase inversion. Any solvent(s) used remains in both the polymer particles and the aqueous phase of the emulsion, and the solvent(s) must then be removed, such as by a vacuum distillation method.
The use of solvents in the above emulsion processes may cause environmental concerns. For example, if the solvent level is not low enough (such as <50 ppm), extensive waste water treatment and solvent remediation may be required. Additionally, the removal of the residual solvents is energy-intense and time-consuming.
U.S. patent application Ser. No. 12/056,529 (Chung, et al.) describes a continuous solvent-free polyester emulsification process using a screw extruder, and is hereby incorporated herein in its entirety by reference.
U.S. Patent Application Publication No. 2007/0059630 (Chen, et al.) describes an emulsion polymerization process, and is hereby incorporated herein in its entirety by reference.
U.S. Patent Application Publication No. 2009/0208864 (Zhou, et al.) describes a solvent-free phase inversion process for producing resin emulsion, and is hereby incorporated herein in its entirety by reference.
U.S. Patent Application Publication No. 2007/0141494 (Zhou, et al.) describes a solvent-free toner making process using phase inversion, and is hereby incorporated herein in its entirety by reference.
A need exists for a process for forming toner particles without the use of environmentally hazardous solvent and without requiring crushing and dissolving of the polycondensation polymer to form an emulsion.